Abstract
We have explained the anomalous eμ events in e+ e- annihilation [1, 2],
+ missing energy as the decay products of a pair of U particles [3] produced in the reaction
This talk has two purposes. (1) The properties of a total sample of 139 anomalous eμ events, Eq. (1), are presented. Previous publications [1–3] were based on a sample of 86 events. (2) These properties are used to test five different general hypotheses as to the nature of the U particle, Eq. (2). We show that among these hypotheses, the only one compatible with all our data is that the U particle is a heavy lepton.
Work supported by the Energy Research and Development Administration.
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References
M. L. Perl et al., Phys. Rev. Letters 35, 1489 (1975).
M. L. Perl in Proceedings of the Canadian Institute of Particle Physics Summer School (McGill University, Montreal, 1975); also issued as SLAC-PUB-1592.
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See G. J. Feldman and M. L. Perl, Physics Reports 19, 235 (1975) for a description of the SLAC-LBL magnetic detector and a review of e+ e- annihilation physics.
A review as of October, 1974 on heavy lepton theories and searches is M. L. Perl and P. Rapidis, SLAC-PUB-1496 (1974) (unpublished).
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An additional argument against any relation of the U particle to charmed mesons is presented in Ref. [16]. There it is shown that in the 3.8 ≤ Ecm ≤4.8 GeV region the eμ events do not cluster in the energy regions where charmed meson production is assummed to be largest — the enhancement in the 4.0 – 4.15 GeV region and the resonance at 4.4 GeV.
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The process ee → eeμμ is a negligible background in the standard e± μ∓ events because experimentally we find very few e± μ± events (Refs. [1] and [3]).
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The term U particle was used as a temporary name for the particles yielding the anomalous eμ events, Ref. [3]. If the conclusions of this paper are accepted a more descriptive name is needed. We would like to reserve ℓ for the general class of leptons, even though the conclusions of this paper would strictly speaking destroy the meaning of the term lepton. If the conclusion that the U particle has leptonic nature remains valid we suggest the use of a lower case tau, τ, for the particle designation; following the μ and v we would like to use lower case Greek letters, and the τ could be the third charged lepton to be found. We feel there will be no confusion with the τ decay mode of the K meson.
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© 1977 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig
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Perl, M.L. (1977). Interpretation of Anomalous e μ Events Produced in e+e- Annihilation. In: Faissner, H., Reithler, H., Zerwas, P. (eds) Proceedings of the International Neutrino Conference Aachen 1976. Vieweg+Teubner Verlag. https://doi.org/10.1007/978-3-322-90614-4_20
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DOI: https://doi.org/10.1007/978-3-322-90614-4_20
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